The following publications are works either authored by our staff or, in some cases, co-authored with people from outside the company.This selection of conference papers and journal articles can be accessed by requesting individual items from our Tonkin + Taylor Ltd Library (email@example.com) or by clicking on the button beside the item. There is no charge for this service. However, please note that our Library follows Library Association (LIANZA) guidelines (link to their guidelines here) and reserves the right not to supply any item if these conditions are not met.
A Review of Shoreline Response Models to Changes in Sea Level
Assessment of current and future coastal hazards is now a legislative requirement in New Zealand
and most parts of Australia. Methods for assessment of erosion hazard are well established, and uncertainty
in the present hazard can be reasonably well estimated. However, uncertainty in defining future
climate-change associated erosion/recession hazard increases due to both the assumptions
surrounding sea-level rise (SLR) as well as limitations of the models used to evaluate the
associated shoreline response. The most widely used methods for defining the coastal erosion hazard
extent utilise a modular approach whereby various independent components are quantified and summed
to provide a final value (e.g. see ). The SLR response component is based on the well-accepted
concept that an elevation in sea level will result in recession of the coastline. This component is
often the largest contributor to erosion hazard zones, so understandably this term is often the
subject of intense debate, media scrutiny and a focus in litigation. With the trends of increasing
populations on the coast this controversy is only likely to escalate. A range of models for
estimating coastal response to changes in sea level have been developed over the past 50 years.
These methods range from the application of basic geometric principles to more complex
process-based assessment. While some methods are used more widely than others, none have been
proven to be categorically correct or adopted universally. While most attention has focussed on the
response of open coast beaches to SLR, other shoreline types including gravel beaches and low
energy coastlines such as lagoons and estuaries are also affected. This paper briefly reviews
existing shoreline response models including the process assumptions, limitations, development and
application history. While most models are based on similar underlying process assumptions,
variation in the definition of model parameters (e.g. closure depth) can produce significant
differences in predicted recession values. As such, robust and informed selection of model
parameters are required to derive defensible conclusions.
All dessed up and no place to flow : a $25 million outfall
A major stormwater upgrade to the pipe network passing through the Ports of Auckland
land was required to reduce upstream flooding and to replace aging infrastructure. Without the
upgrade, drainage improvements to the upstream network (which have already been constructed) would
increase downstream flood risk. Indicative capital costs of the upgrade are approximately $25
Due to construction complexity and hydraulic limitations, a range of design options were considered
by an Early Contractor Involvement (ECI) group that would reduce disruption to the port whilst
providing improved flood resilience. A risk based approach was used to establish the costs and
benefits of the options, so that a realistic hydraulic performance objective could be established
by Auckland Council for the ECI group.
The risk based approach considered the effects of a range of design storms, tailwater levels, and
sea level rise for the different options. The outcomes of the assessment were used to create a
business case that needed to provide both value to existing ratepayers, resilience to future
changes in climate and consider the effects of disruption to the Ports of Auckland.
This paper will focus on the risk based assessment and business case development that formed the
recommendation to the ECI group. It will include discussion on the quantitative risk assessment
including the flood damage assessment, and the economic and qualitative viewpoints encountered
along the way
Challenges designing wet services for Pukeahu National War Memorial Park
The Pukeahu National War Memorial Park was constructed as the Government’s major project to commemorate the centenary of the First World War. In order to build the park, construction of an underpass (the Arras Tunnel) was required to accommodate State Highway 1 (SH1). The Arras Tunnel now carries SH1 traffic west, passing under the Park. This project was completed on budget and ahead of time by the Memorial Park Alliance (the Alliance) driven by effective collaboration between the Alliance (comprising client, contractor and designers) and key stakeholders. This paper outlines some of the challenges, design solutions, and working methods that were important to the success of the wet services design. The key threads that are covered in this paper include:
- Managing a tight urban site with complex and multiple services
- Protection measures for the Tory Street heritage sewer
- Developing a solution for the stormwater overland flows from surrounding streets that enter the tunnel
- Application of sustainable urban drainage approaches for stormwater management in the park
- Resilience of wet services for the Home of Compassion Crèche during a seismic event
- Considering safety in design for construction and operation of assets
- Collaborative team approach.
Adaptable analysis : different approaches that lead to the same results
Analysis of historic records has been, and will continue to be, a reliable means of gaining an
understanding of surface water system behavior. If the design condition under consideration falls within the envelope of historic records, then it is possible to have a high degree of confidence in the analysis results used for design.
However, it is often the case that the set of historic records at a specific site is either
non-existent or does not envelope the range of events for which the design is required. In such
cases a designer will still seek to have a high degree of confidence in the analyses, and
alternative approaches are required.
Such alternative approaches include extrapolation (of observations), detailed analysis using
established hydraulic principles with detailed input data (modelling) and sensitivity assessment
using statistical and other means. All of these approaches are intended for the same end point,
this being a high degree in confidence in results that are to be used in design.
In this paper these approaches are benchmarked against each other using a case study. The results
show that in some cases there are alternative approaches to the detailed hydrological and hydraulic
modelling approach that result in the same end point conclusions being able to be reached
(confidence in results). These alternative approaches will be demonstrated, and in this paper the
relative time inputs to them are discussed using the case study examples.
Keywords: Modelling; Stormwater; Flood level prediction.
Impact of rainwater tanks on the levels of service for water supply in Auckland
Rainwater tanks are a viable alternative water resource option used around the world. Their effectiveness is a function of local climate, uptake, roof and tank size and demand characteristics. Watercare carried out an assessment of rainwater tank potential in the context of the Auckland supply-demand balance to compare them with other water resource options.
The assessment considered their benefits at Watercare’s two relevant Levels of Service, which drive the selection of water sources in Auckland. Ambitious uptake rate scenarios for new and existing properties were developed, which modelled between 23% and 66% of Auckland households having a tank installed by 2050. A synthesized 1000 year rainfall sequence was applied to determine the conjunctive yield of the tanks and Watercare’s lake supply system for the different scenarios of
rainwater tank use.
The work modelled a range of scenarios including the implementation of a programme installing large rainwater tanks on a widespread basis throughout Auckland. Outputs demonstrated that the most favourable scenario would result in tanks supplying up to 16% of the forecast demand at the drought level of service and 35% at the peak level of service. The capital cost of implementation of such a programme would be of four times that of a river source able to supply 100% of the forecast demand
at both levels of service. This paper solely addresses the water resource benefits of rainwater tanks; any wider benefits are excluded.
Transforming Victoria Street : working together to tackle utility design (1)
The Victoria Street Transformation Project has provided Wellington with a tree lined boulevard, enhancing the pedestrian experience with wider footpaths and parks. This has facilitated and encouraged development within the area as well as improved traffic and cycling flows.
The project had a short timeframe from its announcement in September 2014 to its completion by 30
June 2015. In order to achieve these optimistic timeframes, the project was delivered by the
already established and successful Memorial Park Alliance (the Alliance).
The challenge for wet services was to remove, replace and add new components to the water supply,
stormwater and wastewater networks in a busy part of Wellington where these services were critical
to the wider city network. The urban complexity meant that design and construction issues were
inevitable and could only be discovered and solved once the ground was opened up. Further
complications included the need to move services before other elements of the design were complete,
the quantity of services underground, and the need to keep Victoria Street and Vivian Street (State
Highway 1) open at all times.
The Alliance delivery model allowed for close collaboration between the design and construction
teams and the owner, Wellington City Council (WCC). This enabled swift decision making which was
essential to the successful completion of the project. This collaborative approach resulted in
innovative and time-efficient solutions, which had a significant contribution to the project being
completed on time.
Climate change and coastal hazards : a risk-based approach that connects science, engineering and planning
Onehunga foreshore restoration project
Ilaguen 1 - a low head rural run-of-river hydropower project
Climate change and coastal hazards : a risk-based approach that connects science, engineering and planning (1)
Government is proposing to add "the management of significant risks from natural hazards" to Section 6 of the RMA. There is already a strong shift in council practice on managing risk, and the change to Section 6 will mandate and codify a best practice risk-approach.
This paper uses New Zealand examples to illustrate the shift in approach to understanding coastal hazard risks and the impact of climate change. These include experience from Kapiti, Hawke's Bay and Northland and highlight new understanding of the impact of climate change on natural hazards, including the impact of sea level rise on liquefaction susceptibility. They illustrate how hazard and risk information can be presented clearly to aid communities and councils to determine the most appropriate risk management responses.
In addition, the paper demonstrates how the ISO 31000 international risk management standard can be applied to a robust interdisciplinary approach to RMA planning.
Flood risk assessment for a catchment spanning different districts
The Waimapu Stream, which flows into the Tauranga Harbour estuary, has a flood-prone lower catchment area that lies within the Tauranga City area. Most of its catchment, however, lies outside of Tauranga City in the Western Bay of Plenty District. The entire catchment lies within the Bay of Plenty
There has been concern expressed that flooding effects within Tauranga City can be exacerbated by
changes in land use that occur within the Western Bay of Plenty District, over which Tauranga City
Council has little or no control. Collaboration between the different authorities has been
identified as fundamental principle to ensure a sustainable management of the catchment. Bay of
Plenty Regional Council has initiated a Flood Risk Project to develop a Regional Flood Risk
Management Framework and a Regional Flood Risk Management Strategy, using the Waimapu Stream catchment as one of the pilot studies.
Analyses have been undertaken in this catchment in an attempt to quantify the management
constraints as well as opportunities that exist within the overall flood risk framework
implementation. Of significance in the lower catchment are predicted flood depths and
velocity-depth product (used for safety evaluation), while land use practices in the upper
catchment require management to reduce the sediment load to the Tauranga harbour.
In this paper the approach to this pilot study is explained in detail. The study uses a risk-based
assessment for identifying ongoing management of the catchment over the next 100 years to ensure
that the current flood risk is maintained or mitigated to an acceptable level.
Waterview Connection stormwater, streamworks and flood protection
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